Device for measuring the indexnumber of a telegraphic modulation



July 31, 1951 H. M. BAYARD ETAL 2,562,761

` DEVICE FoR MEASURING THE INDEX-NUMBER OF A TELEGRAPHIC MODULATION Original Filed April 5. 1947 2 Sheets-Sheet l d lhn I" 111 4 i s (15.1 +1: O x-. 1

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c12 hm M02 h A @ya July 31, 1951 H. M. BAYARD ET AL 2,552,761

' DEVICE FOR MEASURING THE INDEX-NUMBER OF A TELEGRAPHIC MODULATION Patented July 31., 1951 v venvien-Fon MEASURING THE INDEX- 'NUMBER 0F A TELEGRAPHIC Monof u `LAJrIoN fHontoreM.

Itoguet, Clamart, FranceA Bayard, Meudon, and Raymond J. C."

f. ClltinuatiOlI-Oflabandoned application 739,216, April 3,1947. This application;Ma,y.16,.

1949,.'seria1 No. l 1946?, A

93,618. In France January 9,

.This application isa continuation ofour copending application, Ser. No. 739,216, ledApril 3, 1947, which is now abandoned.` e y v .y

The present invention relates to.. telegraph signal transmission, and,.in particular, to a def vice for measuring .aquantity which is a characteristic of theparticular train of signals being sent over a telegraphlineat a given time, this quantity being called the index number. Y The signals to be considered'are equal length tw0 value code signals, that is, a train of signals of which every signal element has one of two determined values, as plus `unity or minus unity. l l( .The invention will be understood from the Y'following descriptionand the accompanying drawings,..wherein:. e

Fig. .1 shows a particular sequence or train of signal elements constituting part o f :a transmitted message, inV which leach. elementis plus unity or minus unity; l' t j Fig. 2 shows another sequence of signal elements, and how the mantities are determined that are used in the measurement of the characteristics of the signalsequence or train; 4 y

Fig. 3 shows a circuitdiagram of an arranger ment using condensers and a rotary distributor number of preceding signals to be taken into consideration; and. y t.

Fig. 5 is'a circuit diagram of van arrangement using one relay and outof-phase alternating current generators and a wire recorder to measure the index number without any limitation as to the numberiof preceding' signalsto be'taken. in'to consideration. ri E f'" f The International4 Telegraph Committee, at its Brusselsmeeting, proposed the modulation orasignal sequenceof a 4telegraph system:y w .V "i

1. The rate -of formation of the-signals-shall be called modulation rate or telegraph speed, and

the duration in seconds :ofthe unitinterval.'

2. The beginning of a signal velement shall be known as characteristic instant.

Consultative l following deinition for characteristics of the $5 shall be measured inbauds bythe reciprocal of 'f- Further, the same' committee' inserted the 55 tension to three position telegraph modulation.)

We know that eachelementofa modulation can be characterized by a number equal to -1 or +1 according as the element is a spacing'ora marking transmission. A succession an, am,.. am. au of n+1 numbers, of which some equal -1 and the others +1, is an unambiguous dennition of a modulation composed of n+1 elements disposed vbetween `the instant -m, representing the beginning of the element characterized as an, and the instant zero, representing the 'element characterized as au. The index number for this modulation is the quantity represented by It is easy to see that this number m meets our reguirementsinasmuch as it defines clearly and unambiguously any 'given completed modulation. It has the following easily recognized properties:

1. Two diierent number indices correspond to two diiierent nite modulations (i. e. comprising a'nite number of elements): f

2. .The number thus Adefined is included b eytween -2 and +2 if. one takes into account innite modulations, i. e. modulations comprising an innite number of elements before the elementaof` 3. One, and only one, infinite modulation corresponds to any number between -2 and +2;

4. One,' .and only one, finite modulation correspondsto any fractional number between -2 and +2 whosedenominator is a power. of 2;

5. It is observed that an innite modulation corresponds likewise'to such a number; 1

6. An index number included between 0 and +1 corresponds to any modulation terminating at zero instant by an alternation from rest to work (ao=+1, a1=-l) .l

For` greater convenience of lthe following explanation, slightly dierent notations will be adopted 'than that just quoted from the C. C. I. T. recommendations, and c1' will designate the farthest ,back preceding signal considered while Now consider the end of a line whereon a twovalue telegraph current is being received. This current, in general, causes the movement of the armature of a telegraph relay; the successive positions of this armature constitute an uninteran, amd. will becalledthe signal .1.. In other words, if the index number of a modulation or signal train, is known, obtained by taking into account all the signals received since the beginning of the modulation or signal train, it is necessary, to know the index number of this modulation or signal train when the next signal Vhas been'received, to take half the index number already known and to add to it the parameter a of the immediatelypreceding signal received.

It will be seen that in the expression of the index number i as just calculated, the terms become smaller and smaller as they correspond to farther and farther back signals, i. e. as they have been received a longer time before the instant of reception of the most recent signal.

' Therefore, in numerous cases, one can neglect Consider now the diagram of Figurel, which represents an example of a signal modulation receivedv on a telegraph line. At time r, from zero time signal ai, which isvamarking signal, has just been received, therefore At the next characteristic instant, 2f, there has been received, in addition to signal a1, a signal a2 which is a spacing signal (FigQl).H From the above definition, the index number which characterizes the telegraph signal modulation conv sisting of the two successive signals ai and a2 is:

At the next characteristic instant, 3f, 'the three successive signals a1, az, a3 have been received. The index number which corresponds to this signal modulation is At the next characteristic instant, 4r, we should have When h signals have thus been received on the line, that is after a time hf after the beginning of the signal modulation train, we have the index number:

After reception ofthe next signal, i. e. after a -time (n+1) f, the index number becomes:

By comparingl these two expressions, it is seen .that

Thus the value of the index number at` the time when a given signal of `a train ends, is equal to half the value of the index number at the ,time when the immediately previous signal ,ended, increased by the value of the parameter a of the said given signal as above defined.

the remotest terms and take into account only the terms corresponding to a certain number k of the immediately preceding signals received, i. e. the signals which precede immediately the instant at which it is desired to know the index number.

Under such conditions, instead of taking into account, in the determination of the index number at a given instant, al1 the signals which have been received from the beginning of the modulation or train of signals up to said instant, a number which, obviously, increases constantly as new signals are received, account is taken only of a fixed number of signals which occur before a given instant, i. e. a constant number of the immediately preceding signals received before said instant.

To illustrate this case, let us refer again to the diagram of Figure 1, and assume that we wish to take into account only three such preceding signals of the train a1, az, as, a4, as, for the determination of the index number.

' At characteristic instant 3, r from zero time,

the index number i: will be, as before:

At characteristic instant 4, -r from zero time, the index number will be:

No more account is taken of signals ai and az. The value of is is Generally, if at a given instant, (lL-1) signals have been received on the line since the beginning of themodulation, or signal train, but

if account is taken only, for the determination of the index number, of the 1c signals which precede said instant, the index number at that instant has the value When the next signal has been received on the line, ah, the index "number becomes vthe train Thus if one knows, at a given instant t vtaken as zero time, the index number of a telegraph modulation or train of signals, limited to the lc last signals received before that instant', one can obtain the index number corresponding to instant t-i-r at which the next'signal is received by halving the known index number corresponding to instant t, and by adding this half to the difference between the parameter as above defined of the signal arriving at instant t-l-f and the fraction 1/2lc of the parameter of the kth signal received before instant t.

Thus one can, fromone instant to the next, determine the index number of a telegraph modulaltionlor train vof signals atany instant, as theA 'signals constituting said modulation are being received. i An object of the present inventionis toprovide an index number measuring device based on the vabove remarks, and allowing the recording `of the successive values assumed by the indexr number of a telegraph modulation, as the .signals which constitute it are received.

This device of the present invention is Vcharacterized in that it comprises means connected .at the end of the transmission channel on which .the signals are received to record a rst voltage lE1, proportional to the parameter of a signal received on said channel and of the same sign as said signal; means connected to this channel for recording a secondvoltage E2, proportional and Iopposite in sign to the parameter of the 76th signal preceding the received signal, the absolute value of this second voltage being in the ratio withthe first voltage; means for placing these two voltages in series so as to obtain their sum; .means for recording `a quantity proportional to said sum; means. for reducing said quantity to fone-half of its initial Value vduring the interval between the receptions of the two successive signals; means for adding to said half value a quantity proportional to the sum of the two voltages E1 and E2 corresponding tothe next received signal, and means for recording the successive values assumed by the sum Vof said quantities as the signals are received.

The values'thus recorded are then proportional to the successive index numbers of the sequence of signals limited to the last 7c received signals. l

If the number k: of signals selected for the determination of the index number is large, thevoltage recorded, corresponding to the kth sig- ,nal :preceding the lastV signal received, is very small compared to the voltage recorded corresponding to this lastA signal. The value of the index number vlimited to IC preceding signals is then very close to the value of the index number corresponding to an unlimited numberof preceding signals; the difference between these two values may be neglected if a knowledge of the index number is not required with a great precision; this difference may be too small to be detected by the recording galvanometer, anyhow. The device of the present invention may then be simplified by omitting the recording of the voltage corresponding to the lcth preceding signal and by adding directly to half the quantity corresponding to the previous index number the quantity corresponding to the parameter a of the last signal received as above dened.

In Figure 3, A and B designate the incoming terminals of the transmission channel on which the signals are received, and R1 and R2 are two polarized telegraph relays whose windings are connected in series, between terminals AB. The operation of relay R2 is delayed by an interval lcf equal to the duration of lc signals by any suitable means known to the art, such as magnetic shield P.

The right hand and left hand contacts of relay R1 are connected respectively to the positive and to the negative terminals of two sources of direct current each having a voltage E, designated by +E and -E, the other terminals of these sources being connected to ground.

Similarly, the left hand and right hand fixed contacts of relay R2 are connected respectively to the positive and to the negative terminals of two sources of direct current with a voltage designated by E E La ind n the other terminals of said sources being both connected to the armature K1 of relay R1. The armatures K1 and K2 of relays lR1 and R2 are shown in the positions they assume when a positive signal is applied. f

K3 designates a rotary distributor the brush H of which rotates at the rate of one revolution during the duration 1- of one signal, and which' nom'eter GE is connected. Condensers C1 and :C2 have the same capacitance.

:The operation of this deviceof Fig. lows: I It will be assumed-,in lwhat follows, that the application of a positive signal to the windings of the polarized relays R1 and R2 bringsrtheir 3 is as foi- `armatures on to their right hand contacts.

It will also be assumed, by way'of'example, that the train of signals received is that represented 4in Figure l, and that -the number 7c`of preceding signals taken into account for the determination of fthe index number is equal to 3.

When the rst signal, whose parameter (as above defined)A is a1=+1, reaches; at the .instant 'the index number of the rst signals, an error which rapidly becomes negligible. This third contact results in by-passing the sources VAs to relay R1, its armature K1 is thrown onto its right hand contact and is raised to potential a1E=-|E. Assuming that armature K2 is on the just mentioned third contact directly connected to sector I of switch Ka, this potential is applied lto sector I of the switch K3 and, by brush B to the condenser C1 which takes on a momentary charge Ca1E=+CE.

When brush E rotates and reaches contact 2, the condenser C1 is placed in parallel with the condenser Cz having an equal capacity. The condenser C2 takes on a charge (llCE cz- 2 which is proportional to the index number i1 of the first signal a1 since, this signal not being preceded by any other, its index number i1 is necessarily equal to its parameter a1. Thus one has,v after the charges divide, for the charge of condenser C1, the quantity The grid of the tube M is raised to a potential V1, proportional to this charge Q1, and the recording galvanometer GE' shows a certain current proportional to this potential V1, supposing the characteristic of the tube to be linear; thus, nally, the registered galvanometer current is proportional to the index number i1.

At instant lr, after the zero instant the second signal, whose parameter as above defined is a2=-1, (Fig. 1) is received by relay R1. The armature K1 of the latter is thrown on to its left hand contact and is raised to the potential va11E=E proportional to the parameter az of the second signal. It is still assumed that K2 is on its third contact.

This voltage is applied by the sector I and the brush B of rotary distributor K3 to the condenser C1 which takes on a momentary charge of magnitude CazE, proportional to the parameter az. The residual charge (MGE 2 which had been received and retained by the condenser C2 during the previous signal and divides into equal parts between condenses C11 and Cz which thus have, each, a total charge 1 Q3=2'CE g21-la3 which, precisely, from the denition of the index ecc number, is proportional to the index number lz of the two rst signals a1 and a2. that is:

l QT-Qzz the recording galvanometer, then registers a new current intensity which is proportional to this new index number iz.

Similarly, when the third signal a3=1 (Fig. l) is received by relay R1 from sector I, the condenser C1 takes on a charge a3CE=CE and then when the vbrush B rotates and again comes to sector 2, this charge aaCE combines with the residual charge- WGW) and the whole charge divides equally between condensers C1 and Cz which thus, each have a charge Qa=2(aa+a22+g which, as can be seen from the definition given of the index number, is proportional to the index number is of the three rst signals The recording galvanometer thus registers a. new current intensity proportional to the index number is. It is still assumed that armature Ka is on its third contact.

'I'he same process of division and accumulation of charges on the condensers would thus be repeated upon the beginning of the reception of each successive signal, the recurrence law above given being observed each time, so that a recording would be obtained of the succession of index numbers relative to the whole train of the received signals, taking into account, each time the whole sequence of these signals if no relay Rz were used. The function of relay Rz which has been used, however, as stated, is to limit the number of the preceding signals which are in volved in the determination of the index number.

In. the example which has been given, this number of preceding signals has been selected equal to three, so that R2 did not enter into action during the first three signals. It is still assumed that during this interval the armature Kn has remained on its third contact.

Relay R2 thus having its operation delayed for the duration of three signals, when the fourth signal a4=+1 is received by relay R1 at the end. of time interval 3f, the relay Rz operates under the action of the rst signal a1=+1, and its armature K2 is thrown from its third contact onto its right hand contact where it is raised to a potential This potential adds algebraically to that of the armature K1 of relay R1, so that the sector I of rotary distributor Ka is raised to a potential and the condenser C1 receives a charge This charge is in addition to the residual charge This expression is in good correspondence with nthe law of recurrence given above in which h=l4 and llc=3.

1 Q4=CEZ4 thus represents accurately except for the factor 1/2CE the index numberii 'of the modulation or signal train considered atthe time of the recep-r tion of the fourth signal since'the beginning of the transmission, and limited to signals received.

Similarly, at the next characteristic instant at the end of time interval 4f, we would have af same will hold for the following signals. The currents registered by the recordingy galvanometer are thus actually proportional to the suc-V cession of the index numbers.

In practice, as already stated, relay Rz of Fig. 3 comprises no third contact directly connected to sector I of rotary distributor Ka. The result is that the measurement of the 7c (three) first index numbers is erroneous, since one adds algebraically to voltage E from relay R1 a voltage whose sign may be either positive or negative, a priori, inasmuch as the armature of R2 may just as well have been left, at the end of the. previous signal transmitted, on either one or the other of its two positions. However, since, the effect of the preceding signals on the value of the index` number decreases rapidly according as toA how bar back a given signal was applied, this error becomes rapidly negligible. By way of example, if one takes the number of previous signalelements considered lc=3, the error on the 8th index number measured is smaller than A i. e. at most equal to onequarter of the smallest the last-,three diierence between any two index numbers. Now

which gives, consequently, the entire sequence of the index numbers corresponding to all the signals received since the beginning of the signal train transmission, with no limitation to the 101 number of said preceding signals, considered. which limitation exists in the device ofFigure'S, to the lc immediately preceding signals received asl of the time of measurement.

Figure 5 shows a modification, wherein'v the recording of the quantities proportional to the successive index numbers (relative to an unlimited number of preceding signals) is effected by Vmeans of a magnetic wire instead of con? densers. l

In this Figure 5, A and B designate, as previously, the ends of the transmission channel. and R1 the polarized telegraph relay connected to said channel. The two contacts of this relay are respectively connected to two generators, G1 and G2 which respectively supply alternating currents having between them a phase difference of One or the other of these two generators, according to the position of the armature K1 of relay R1 supplies, through a transformer having windings S1, S2 the printing coil I'of a'magnetic wire recording system my. 'I'he readerf printing coil L of this system is placed at such a distance from the coil I along the length of the wire that the point of the wire which has been impressed by printing coil I is, after an interval of time equal to the duration of one signal 1,' facing the reading'coil L; this reading coil Lis then the seat of an induced current pro portional and also to the variation of the magnetic condition of the wire my, i.e. to the intensity of the current in the printing coil I which caused this variation. This reading coil L is connected, to a recording galvanometer GE, to a wind S4, coupled on one side with a winding S1 and on the other side with a winding S3 which isv in series with a winding Sz'coupled to winding S1. The current'in the reading coil L is adjusted in'such' a ymanner as to be equal to half the cur-` rent it has beennecessary to pass through the printing coil'Ito cause the magnetic wire to be impressed in desired manner; on the other hand the current sent 4by the reading coil L through thefwinding S4 is adjusted so as to Vbe in phase with'the current induced in this same winding by means'of S1`,*by one of the'two generators, G1 for' example. j V

Thefoperatio'n of 'this device is as follows: when a signal received, the armature K1 of the relay R1 is thrown onto one of the two contacts u, w, of this relay, according to the polarity of said received signal; the corresponding generator, G1 for instance, is put into circuit and sends into galvanometer GE, through windings S1 and S4, a current of a certain intensity. At this same time. the point of the wire which had been impressed by the action of the preceding signal in applying energy-from generator G1 to printing coil I, is facing the reading coil L; it. induces in this coil L a current -whose value is half that of the current which had been sent into the printing coil I -under'the action of said preceding signal; thisl induced current is also sent to the recording galvanometer GE.

Thisflatter thus records the sum of two cur:- rent intensities: on the one hand a current cor. responding to the signal being received, on the other hand half of the value of the current `corresponding to the immediately preceding signal; this is the-recurrence law indicated above, and the succession ofthe intensities recorded, provided a calibration has first been eiected, gives the sequence of the 'index numbers. y

The magnetic Wire could be replaced'by any recordingldevice, a film or a disc forinstance.

asta-i612 what we'ciaim is:

l. VA device for recording thesuccessive values assumedA by the indexfnumberof a' sequence off two-value telegraph signals received at the end of a transmission channel, in step with the reception of said signals, said sequence being limited to' the k last signals received, 7c being a xed number, this device comprising a first telegraph r'elay connected to the end of the transmission. channel for recording a iirst voltage E1 proportional to the parameter of the signal received and ofthe same sign as the latter, a second telegraph relay connected to the end of the transmission channel for recording a iirst voltage E1 proportional and of opposite sign tothe parameter of the kth signal preceding the signal being received, this second voltage `being in the ratio with the said iirstvoltage, means for placing the two said voltages inseries so as to obtain their sum; means for recording a quantity propor-r tional to said sum, means for reducing' said quantity to half its initial value, during the interval between the receptions of two consecutive signals, means for adding to said half a quantity proportional to the sum of the said two voltages E1 and E2 corresponding to the next signal received, and means for recording the successive values assumed by the sum of said quantities in step with the reception of the signals, values which are proportional to the successive index numbers of the signal sequence limited to the lc just preceding signals received.

2. A device for recording the successive values assumed by the index number of a'sequence of two value telegraph signals, received at the end of a transmission channeLin step with the reception of said signals,'said sequence being limited to the k just preceding signalsreceived, 1c being a fixed number, this device 'comprising a iirst condenser, means for applying to saidrst condenser the sum of two voltages:` )a iirsiiv voltage having the Same sign as theimmediately7 preceding signal received and' a second vvoltage having a sign opposite to that of the kth signal immediately preceding the last preceding signal received.' said second voltage being in the ratio with said first voltage, a second condenser having the same capacitance as said first condenser, means for temporarily insulating said rst condenser from said voltage sources during a short time after the reception of each said signal, and for connecting it in parallel with said second condenser and means for recording at each of these parallel connections the maximum potential difference between the terminals of said condensers, said potential diierence being proportional to the successive valuesV assumed by the index number of the .sequence of the k immediately preceding signals received.

3. In a device for registering the successive values of the index numbers of an incoming received train of two-value telegraph code signals of equal length, a receiving relay having an armature and two fixed contacts, two sources of elec- -trical energy each having' one terminal con'- nected to one of said fixed contacts, said two sources having at a given instant voltages of equal magnitude and opposite polarity, a galvanometer having an 'actuating winding.' electrical energy translating -means'- having input`= i to the actuating winding of said galvanometer.

said electrical energy translating means being adapted to deliver to saidv outputy terminals :a: :first electrical current whose electrical characteristics are determined by which one of said xed contacts is at that instant engaged by said armature, dueto the signal then being received; said translating means comprising timed signal storing and modifying m'eans for storing successive signals and adapted atveach characteristie -'instant of the beginning of a new signal interval to halve vthe record of the signal immediately'precedi'ng the' signal being received at that instant and to 'deliver to said output terminals superposed on said iirst Ielectrical current, a second electrical current whose electrical characteristics are determined by said so halved record of said immediately preceding signal. 4. In a device for registering the successive values of the index numbers ,ofY an incoming received train ofl two-valueftelegraph code signals of equal length, a receivingA relay having an armature Vand two fixed contacts, aufrst direct current Asource having its positive terminal connected to a iirst said iixed contact, a second direct current source havingits negative terminal connected toa second said fixed contact, a -timed rotary distributor having airotating brush and a long contact sector and a short contact sector and making one rotation during the interval of one signal, said long sector being connected to said armature, a nrst condenser connected between said brush and the second terminals of said sources, a second condenser having the same capacitance as said first condenser connected between said short sectorL and the second terminals of said sources, a galvanometer having an actuating winding, and amplifying means having its input connected to Vsaid short sector and its output connected to the actuating winding of said galvanometer. A

, 5. In a device for registering the successive values of .the index numbers of an incoming receivedA train of two value telegraph code signals of equal length, taking into consideration only a deinite limited number 1c of preceding signals, a iirst receiving relay having an actuating winding and an armature and two fixed contacts, a nrst direct current source'pf voltage E having its positive terminal connected to a first said fixed contact, a second direct. current source having its negative terminal connected to a second said fixed contact, a second receiving relay having an actuating winding and an armature and twov stationary contacts, saidactuating windings of said relays beingconnected in series, said second-relay comprising signal retarding means adapted to retard the response ofthe armaturey of said second relay to the. application. of a signal Yto its winding for a time interval. .equalto k signal lengths, a third direct current source of voltage having its positive terminal connected to a first said stationary contact, a fourth direct current source of voltage Having 'its' negative ternunaieonnected to a second saidstationary contact, the second terminals of said third and fourth sources being connected in common -to the armature of said first relay, a timed rotary distributor having a rotating brush and a long contact sector and a short contact sector and making one rotation during the interval of one signal, said long sector being connected to the armature of said second relay, a rst condenser connected between said brush and the second terminals of said first and second sources, a second condenser having the same capacitance as said rst condenser connected between said short sector and the second terminals of said first and second sources, a galvanorneter having an actuating winding, and amplifying means having its input connected to said short sector and its output connected to the actuating Winding of said galvanometer.

6. In a device for registering the successive values of the index numbers of an incoming received train of two-value telegraph code signals of equal length, a receiving relay having an armature and two fixed contacts, two alternating current sources of the same frequency having a phase difference of 180, each of said sources having one terminal respectively connected to a said fixed contact in such manner that the voltages on said fixed contacts at any given instant are 180 out of phase, a galvanometer having an actuating winding element, a iirst winding connected between the armature of said relay and the second terminals in common of said sources,

a second winding inductively coupled to said first winding, a uniformly traveling magnetic wire, a recording coil and a reproducing coil spaced mutually apart and in magnetic relation to said wire, the spacing between said coils being the distance traveled by a point on said wire during the length of one signal, said second winding being connected to said recording coil, said reproducing coil being connected to the actuating winding element of said galvanometer, and a third winding connected to the actuating winding element of said galvanometer and being inductively coupled to said first winding, the current delivered by said reproducing coil to said actuating winding element being adjusted to be in phase with the current delivered to said actuating winding element by said third winding and of magnitude equal to one-half the magnitude of the current so delivered by said third winding to said actuating winding element.

HONOR M. BAYARD. RAYMOND J. CH. ROQUET.

REFERENCES CITED Y The following references are of record in the file. of this patent:

UNITED STATES PATENTS Name Date Sunstein July 26, 1949 Pernic -..7 Nov. 21, 1950 Number 

